The present invention relates to a control program for display apparatus.
Relatively high-performance central processing unit or an image processing processor is necessary for an image display apparatus such as computer game machine when a moving solid body is to be displayed.
While, when the image display apparatus is limited in hardware performance or high-performance processor is not available, pretended solid bodies are expressed by sprite or other image processing methods of not so heavy calculation.
Sprite is an image processing method that a two-dimensional image pattern (sprite image) is prepared, then the image is displayed at a predetermined position. The sprite image is enlarged, diminished or rotated so as to express a pretended solid body.
There are some image processing methods of not so heavy calculation for expressing solid bodies. First of them is shown for example in Japanese Patent Application 09-305795, that is, a symbol body moving between right and left walls is expressed by changing extraction or contraction ratio of the walls in response to a view point of the symbol body.
The second is shown for example in the Japanese Patent Application 07-312721, that is, an image frame displayed is transformed into a sprite image before the image frame is displayed, the sprite image is pasted on various surfaces of a polyhedron and the polyhedron is rotated.
In order to realize the conventional image processing method, an image processing machine for executing the image processing method freely positions four vertexes of the sprite image. However, since the image processing machine must be of high performance in image processing, the construction becomes complicated and the cost increases.
So, in another conventional machine which must be of low price such as portable game machine, three vertexes of a sprite image can be positioned for deforming a rectangle into a parallelogram or a rhombus. The conventional machine of this type cannot execute the conventional image processing method.